Tiff Files in Deep Sky Stacker

[Tommohawk]

I have a few queries re tiff files in DSS and hope someone can explain.

Firstly, it took me forever to figure out that the autosave tiff file cannot be opened using normal editing software because its 32 bit. At least I think that is the case – maybe someone could kindly confirm.

Second, when the final image is rendered on the screen, it seems to be quite dark. Of course this can be edited within DSS, and I’ve found stacking the RGB curves somewhere in the middle of the graph seems to get a good result. So then I save this file as a 16 bit image, and play with it in editing app. That works OK.

But if I close the image in DSS and then re-open the 32 bit autosave file, it looks quite different to the way it was originally rendered. I also notice that the graph now looks like a straight line, rather than the original curvy line. If I hit the “reset” button, the curve appears as it did in the original, and if applied, the image then darkens to the same appearance it had in the original. I don’t know why this should be, but the key question is, if I reopen the 32bit autosave file, will this have the same data as the original? Or do I need to do all my DSS manipulation before closing the original file?

I hope that makes sense! Thanks for reading.

[Langy]

As far as I am aware the Autosave file is the file that gets created when the stacking has completed.

I always treat that file as an original and any further changes always do a save to file. Sometimes I alter the settings in DSS with the curves etc. and sometimes I may just do a save to file straight away and then do that in PS.

[Tommohawk]

As far as I am aware the Autosave file is the file that gets created when the stacking has completed.

I always treat that file as an original and any further changes always do a save to file. Sometimes I alter the settings in DSS with the curves etc. and sometimes I may just do a save to file straight away and then do that in PS.

OK thanks for that. Main thing to know is that if I do a quick stack eg at session end I can always reopen the autosave file to edit further without losing anything.

Whilst on this, I have another related query. If I restack the lights, maybe having deleted some dodgy ones, do I need to include all the darks/bias, or just the masters? Main reason for asking is that I'm taking up a huge amount of file space and would be good to delete unneeded stuff as I go.

Cheers

Tom

[Langy]

Not being 100% but I would guess that the Lights are first processed to align them and check which the software can use.

After that selection the Darks and Bias frames are then used to exclude content from the lights.

The darks should be taken at the time of the lights as they are a comparison of the chip content with the same conditions. However the Bias frames as they are at the fastest shutter speed possibly may be able to be used for other stacks.

If did the BeeHive cluster last night at 25 second exposures, forgot to take the Darks so used some others I took last night at either 15 seconds or 45 seconds. Just did one lot of Bias frames to cover the whole night.

http://nova.astrometry.net/image/530741

[Tommohawk]

Not being 100% but I would guess that the Lights are first processed to align them and check which the software can use.

After that selection the Darks and Bias frames are then used to exclude content from the lights.

The darks should be taken at the time of the lights as they are a comparison of the chip content with the same conditions. However the Bias frames as they are at the fastest shutter speed possibly may be able to be used for other stacks.

If did the BeeHive cluster last night at 25 second exposures, forgot to take the Darks so used some others I took last night at either 15 seconds or 45 seconds. Just did one lot of Bias frames to cover the whole night.

http://nova.astrometry.net/image/530741

Yes I get the idea about when to take darks/flats/bias, what I meant was that having got them, and processed everything once, if i decide to re-process, do I need to reload all the darks/flats/bias, or just the master dark etc? If the latter, then I can delete all the original individual darks and just keep the masters to save files space.

Nice image!  I'm just playing with my first effort at Pinwheel galaxy done last night. I'll  post it when its done. 

[ChrisLX200]

When the stack is finished use the option on the left 'Save Picture as File' and choose 16-bit TIFF. You should find that will open in PS OK.

ChrisH

[dph1nm]

You can just reload the masters.

NigelM

[Langy]

Yes I get the idea about when to take darks/flats/bias, what I meant was that having got them, and processed everything once, if i decide to re-process, do I need to reload all the darks/flats/bias, or just the master dark etc? If the latter, then I can delete all the original individual darks and just keep the masters to save files space.

Nice image!  I'm just playing with my first effort at Pinwheel galaxy done last night. I'll  post it when its done. 

Yes I answered what I thought you may need in the first two lines.

[Tommohawk]

OK thats great, thanks all.